There is a known virtualization technology in which a hypervisor manages the machine resources of a single server and multiple virtual machines are operated in parallel on the server. In this virtualization technology, in order for the server to efficiently use the machine resources of the server, the management server that manages the server moves a running virtual machine from one server to another server in an uninterrupted manner. This is referred to as a “live migration”.
In a live migration, the management server copies a memory image of the move source to the move destination. Because the memory in the running virtual machine continues to be changed, strictly speaking, it is inevitable that the virtual machine temporarily fails (stops) at some point while the management server is performing the copying. This temporary downtime (hereinafter, referred to as a “downtime”) usually lasts for several seconds; however, it depends on the usage state of the resource of the virtual machine that is to be moved. Consequently, if the virtual machine is moved when a large amount of resource is being used, it takes a long time, e.g., several seconds or more.
Consequently, there is a disclosed technology for avoiding the occurrence of a failure for a long time due to a live migration. In this technology, the management server uses a high-degree equation to predict the resource usage of a physical server that will be used in the future. When the management server predicts the occurrence of a resource shortage, if a time zone is present where the resource usage does not exceed a move threshold for defining an upper limit of the movement related to a load and if a move time of the move virtual machine that is moved is included in this time zone, the management server moves the move virtual machine in this time zone.
Patent Document 1: Japanese Laid-open Patent Publication No. 2010-117760
However, even when it is predicted that the resource usage in the physical server will run short, if no time zone is present in which the resource usage of the virtual machine running on the physical server below the move threshold, the moving of the virtual machine running on the physical server is limited. Consequently, there is a problem in that the operation of the physical server whose resource usage is predicted to be in short supply may possibly become unstable in the future.